countering human-paid spammers

after i patched up recaptcha in my community, it seems spam is still coming from nowhere and the only thing i can 开发者_运维百科imagine causing it is a paid human being to spam, any ideas how to prevent these bastards ?

Other than IP blocking, which isn't very effective, I would suggest using a community effort like StackOverflow uses. Allow users to flag content, and it will help the problem.

You can also require unique email with an activation link, if you don't already.